This invention relates to liquid cyclopentadienyltrimethylplatinum compounds, a process for producing a film, coating or powder therefrom and a one pot method for producing an organometallic compound.
Chemical vapor deposition methods are employed to form films of material on substrates such as wafers or other surfaces during the manufacture or processing of semiconductors. In chemical vapor deposition, a chemical vapor deposition precursor, also known as a chemical vapor deposition chemical compound, is decomposed thermally, chemically, photochemically or by plasma activation, to form a thin film having a desired composition. For instance, a vapor phase chemical vapor deposition precursor can be contacted with a substrate that is heated to a temperature higher than the decomposition temperature of the precursor, to form a metal or metal oxide film on the substrate.
Preferably, chemical vapor deposition precursors are volatile, heat decomposable and capable of producing uniform films under chemical vapor deposition conditions. In producing thin films by chemical vapor deposition processes, precursors that are liquid at room temperature, rather than solids, often are preferred.
Cyclopentadienyltrimethylplatinum compounds are very promising platinum (Pt) chemical vapor deposition precursors. Chemical vapor deposition is a technique for depositing metal films onto a surface. Although chemical vapor deposition precursors are usually preferred in the liquid state, two of the most utilized platinum species, the parent complex (cyclopentadienyl)trimethylplatinum (mp=109xc2x0 C.) and (methylcyclopentadienyl)trimethylplatinum (mp=30xc2x0 C.), are both solids (Xue et al. J. Am. Chem. Soc. 1989, 111, 8779). Liquid precursors are in most cases easier to deliver and can give more consistent vaporization (i.e., solids may vary in surface area, particle size, and crystallinity which may affect uniform volatility).
The liquid cyclopentadienyltrimethylplatinum complex (ethylcyclopentadienyl)trimethylplatinum has been disclosed in U.S. Pat. No. 5,929,267, where it was utilized to form platinum films. The compound was characterized by 1H NMR and CH analysis. Estimates of melting point ( less than xe2x88x9278xc2x0 C.), density (xcx9c1.5 g/cm3), and viscosity (xcx9c5 cP) are included. Trace metals analysis indicates impurities in the low ppm range. TG-DTA indicates approximately 0% non-volatile residue. The vapor pressure was found to be 0.3 torr at 50-55xc2x0 C. The compound is reported to be stable to air and water, as well as to temperatures up to 150xc2x0 C. (although no half-life data was presented). The yield for this precursor, however, is moderate at 51% from iodotrimethylplatinum.
Also, synthesizing organometallic platinum compounds on a large scale basis has not been disclosed. Cyclopentadienyltrimethylplatinum complexes have been synthesized from Pt(IV) (e.g., K2PtCl6) and Pt(II) (e.g., K2PtCl4) sources. However, both routes proceed through a Pt(IV) trimethyl species of the general formula [XPt(CH3)3]4 (X=halide (e.g., I))(see FIG. 1, Path A). This tetramer can be made increasingly reactive by adding a halide metathesis reagent such as a silver salt (e.g., silver triflate). Isolation of the tetrameric species is commonly achieved via extraction, precipitation, trituration, and filtration. This tetrameric compound can then be used for the formation of a number of other trimethylplatinum containing compounds, including the cyclopentadienyl moieties. No attempt to synthesize a cyclopentadienyltrimethylplatinum complex by a direct route from K2PtCl6 or K2PtCl4, without isolation of an intermediate as discussed above, has been disclosed.
In developing methods for forming thin films by chemical vapor deposition methods, a need continues to exist for chemical vapor deposition precursors that preferably are liquid at room temperature, have relatively high vapor pressure and can form uniform films. Therefore, a need continues to exist for developing new compounds and for exploring their potential as chemical vapor deposition precursors for film depositions. It would therefore be desirable in the art to provide a chemical vapor deposition precursor in liquid form and producable with high yields, for example, a liquid cyclopentadienyltrimethylplatinum precursor.
Also, it would be a significant advancement in the art to provide a method capable for a scale up production of organometallic platinum compounds with significant platinum recovery. Further, it would be a significant advancement in the art to synthesize a organometallic platinum compounds using a one step process where all manipulations are carried out in a single vessel, and which route to this family of compounds does not require the isolation of an intermediate complex.
This invention relates in part to liquid cyclopentadienyltrimethylplatinum compounds selected from (isopropylcyclopentadienyl)trimethylplatinum and (tert-butylcyclopentadienyl)trimethylplatinum. This invention also relates in part to a process for producing a film, coating or powder by decomposing a cyclopentadienyltrimethylplatinum compound precursor selected from (isopropylcyclopentadienyl)trimethylplatinum and (tert-butylcyclopentadienyl)-trimethylplatinum, thereby producing the film, coating or powder. This invention further relates in part to a one pot method for producing an organometallic compound comprising reacting a metal source compound, an alkylating agent and a hydrocarbon or heteroatom-containing compound, e.g., cyclopentadienyl compound, under reaction conditions sufficient to produce said organometallic compound.
The invention has several advantages. For example, the method of the invention is useful in generating organometallic compound precursors that have varied chemical structures and physical properties. The method can be employed to produce organometallic compounds, such as, for instance, cyclopentadienyltrimethylplatinum compounds. The method of the invention is capable for a scale up production of organometallic platinum compounds with significant platinum recovery. The method is particularly well-suited for scale-up production since it can be conducted using the same equipment, some of the same reagents and process parameters that can easily be adapted to manufacture a wide range of products. The method provides for the synthesis of organometallic compounds using a one step process where all manipulations are carried out in a single vessel, and which route to this family of compounds does not require the isolation of an intermediate complex.